Scientists at the University of Würzburg in Germany have found a way to produce and isolate oxoboranes, an unusual class of molecules that researchers have considered too unstable to study under ordinary laboratory conditions. The discovery, published in Nature Chemistry, resolves a chemistry problem that has remained open for more than 60 years and could provide access to other elusive compounds.
Overcoming a long-standing chemistry challenge
The research was led by Professor Holger Braunschweig, with computational support from a team led by Professor Ashwini K. Phukan of Tezpur University in India.
Boron rarely forms triple bonds, in which two atoms share three pairs of electrons. For more than 15 years, Braunschweig has investigated ways to overcome this limitation and create molecules with unusual bonds involving boron.
His laboratory reported the first molecule containing a triple bond between two boron atoms in 2012. In 2025, researchers achieved another milestone by producing the first neutral molecule with a triple bond between boron and carbon.
One major challenge remained among the elements in the first row of the p-block of the periodic table: isolating a stable organic oxoborane, a molecule characterized by a triple bond between boron and oxygen.
Chemists have studied oxoboranes since at least the early 1960s. Researchers working in both organic and inorganic chemistry have detected and trapped these compounds under extreme conditions, while other experiments have provided indirect evidence of their existence. Several related derivatives have also been produced, but stable oxoboranes that could be isolated and examined remained out of reach.
Unexpected reactions reveal elusive molecules
The breakthrough came from an experiment that was initially intended to investigate a different chemical reaction. University of Würzburg PhD students Lukas Lupczyk and Christian Markl were independently studying how a compound called diboracumulene reacts with various ketones, which are commonly used in organic synthesis.
The researchers observed an unexpected result: the reactions produced a characteristic orange or yellow solid. Oxoborane was the main product, even though other chemical outcomes had appeared more likely.
“This discovery was a pleasant surprise. I had no idea that diboracumulene would react in this way, let alone with several different simple substrates. And when Christian came to me with the compound, I knew we were on to something,” says Lukas Lubczyk.
The result was particularly striking because oxoboranes had resisted isolation attempts for decades. The experiments showed that they could form unexpectedly from reactions involving relatively simple starting materials and persist long enough to be studied.
“Almost everyone in the field had given up on oxoboranes because they were thought to be too unstable to isolate. So we were stunned to see that oxoboranes formed spontaneously in these reactions and persisted long enough to be studied,” says Holger Braunschweig.
A potential route to rare compounds
Using the newly identified method, the scientists prepared three different oxoboranes. The fact that the approach worked with multiple compounds suggests that it could provide access to a wider range of oxoboranes that have previously been difficult to isolate.
The research team is now investigating how broadly the method can be applied. The scientists hope to produce additional oxoboranes and determine whether a similar strategy could generate other elusive compounds containing elements from across the periodic table.
The finding addresses a chemistry problem that has challenged researchers for more than 60 years and demonstrates how unexpected reactions can reveal chemical possibilities once considered inaccessible.
International collaboration and funding
The work was carried out by the Würzburg research team in collaboration with researchers led by Professor Ashwini K. Phukan at Tezpur University in India. Phukan’s computational research supported the study.
The project received funding from the German Research Foundation (DFG), the German Academic Exchange Service (DAAD), and India’s Department of Science and Technology (DST).
Source: www.sciencedaily.com
